Size-controlled lignin nanoparticles for tuning the mechanical properties of poly(vinyl alcohol)

Lignin nanoparticles (LNPs) are regarded as a sustainable and advanced way to use residual lignin for application in composites. However, some challenges remain to achieve the controllable preparation of LNPs or tuning the polymeric properties with LNPs. In this study, size-controlled LNPs were prepared with three narrow lignin fractions, then added into poly(vinyl alcohol) (PVA) matrix. LNPs and different LNPs-filled PVA, analyzed by GPC, 31P NMR, and 2D HSQC NMR, TEM, rheology and tensile tests, revealed substantial differences in terms of lignin structures-LNPs sizes-PVA mechanical properties. With the addition of fractionated LNPs (LNPs70), the toughness and strength of PVA can be improved to 6.33 % and 289.9 %, respectively. This study will promote the development of not only advanced hydrogels but also lignin chemistry and biorefinery technologies.